19
Neutral Hydrogen in Galaxies NGC 6946 In grey we see the stars In blue the emission from the atomic hydrogen (21-cm line). Hydrogen is much more extended than stars. The rotation of hydrogen has been crucial to infer the existence of dark matter.

21
Major discoveries Over the years, there have been four Nobel Prizes in Physics given to radio astronomers… These were given for the discovery and study of sources that are esentially detectable only at radio wavelengths.

24
As a matter of fact… We already mentioned that the discovery of radio waves from space resulted from trying to solve a problem of telecommunications. The discovery of the cosmic microwave background also came from studying a problem of telecommunications.

35
Advantages of an interferometer Better angular resolution Can produce images with millions of pixels Substitute steel with electronics Provide positions with amazing precision However, they are complex and hard to maintain, and require detectors that preserve the phase information of the signal, for example, HEMT (High Electron Mobility Transistors) and SIS (Superconducting-Insulator-Superconducting) devices.

45
Radio astronomy in Mexico Only about 150 astronomers in total in Mexico. A dozen of them focused in radio astronomy (observations and theory). Observers use radio telescopes in other countries (USA, Europe, Japan, Australia) to do their work.

50
But, what can be consider the biggest achievement of radio astronomy? Beyond the specific discoveries, radio astronomy persuaded astronomers that it was worthwhile to study the Universe outside the optical window…

62
Atacama Large Millimeter Array Located in Chajnantor, Chile in the Atacama desert at 5,000 meters of elevation. 64 antennas in final array. Financed by North America, Europe, Japan and Taiwan at a cost of 1.4 billion US dollars. Mexican radio astronomers will have competitive access to ALMA (we published second paper with ALMA data).